1. Field of the Invention
The present invention relates to a maintenance method for a liquid jetting apparatus, in particular, an idle suction method for sucking and discharging a liquid accumulated in a cap after performing a purge by covering a jetting head provided for a liquid jetting apparatus with the cap, and the liquid jetting apparatus.
2. Description of the Related Art
In the conventional liquid jetting apparatus exemplified by a printer apparatus based on the ink-jet system, for example, a plurality of nozzle holes are formed on a nozzle surface of a jetting head, and a liquid such as an ink or the like is jetted from the nozzle holes. When the liquid jetting apparatus is used after a long period of time in which the liquid jetting apparatus is not used, the purge process is performed to suck out the remaining liquid by a suction pump in order to discard any deteriorated liquid remaining in the nozzle holes of the jetting head.
In order to perform the purge process, for example, the conventional ink-jet printer is provided with a cap for covering the nozzle surface. Further, a discharge hole, which is formed at a bottom portion of the cap, is connected to the suction pump via an ink flow passage. The suction pump is driven to generate the negative pressure in the cap in a state that the nozzle surface is covered with the cap so that the nozzle holes are surrounded inside. Accordingly, the purge process is performed, in which the liquid in the nozzle holes is sucked out into the cap.
If the liquid, which is accumulated in the cap by the purge process, is remained as it is, the liquid-accommodating capacity in the cap is lowered when the next purge process is performed. Further, the discharge hole formed at the bottom portion of the cap and the ink flow passage may be clogged up. A possibility arises such that the purge process cannot be executed appropriately in the next time and the followings. Therefore, in the conventional ink-jet printer, the suction pump is driven (to perform the idle suction) in a state that the cap is separated from the nozzle surface after completing the purge process, and thus the liquid, which is accumulated in the cap, is discharged to the outside of the cap via a tube.
When the idle suction is executed, if the suction speed (i.e., the pump suction amount per unit time) is not appropriate, then the opening, which is communicated with the discharge hole, is formed at the liquid surface of the liquid accumulated on the inner bottom portion of the cap in some cases.
If such an opening is formed, even when the suction pump is driven to perform the idle suction, then only the air is sucked through the opening. Once the suction of the air starts through the opening, the movement of the surrounding liquid, which is to be brought about in the direction to close the opening, is inhibited by the flow of the air. As a result, the opening is hardly closed. Therefore, the period of time, in which only the air is sucked, is prolonged, and it is difficult to efficiently discharge the liquid contained in the cap.
It is considered that such a phenomenon results from the viscosity (fluidity) of the liquid and the suction speed of the pump. The liquid jetting apparatus is used in a variety of temperature environments. The liquid jetting apparatus is used in a relatively low temperature environment in some cases, and the liquid jetting apparatus is used in a relatively high temperature environment in other cases. The viscosity of the liquid (especially the ink) is changed depending on the temperature environment in which the liquid jetting apparatus is used. Therefore, if the suction speed during the idle suction is constant, for example, when the liquid jetting apparatus is used in a low temperature environment in which the viscosity of the liquid is high, then a possibility arises such that the idle suction cannot be performed appropriately. It is affirmed that such a circumstance also arises similarly in any liquid jetting apparatus for jetting any other liquid, without being limited to the printer apparatus for jetting the ink.